Text messaging has become a very popular mode of communication in many wireless communication networks. One example of text messaging is Short Message Service (SMS), which is a communication protocol allowing the exchange of short text messages (i.e., 160 characters) between mobile devices. While the term “text message” traditionally referred to text-only messages sent using SMS, it has been extended to include multimedia messages, such as images, video, sound content, etc. The multimedia messages may be sent using Multimedia Message Service (MMS) protocol. Often times, mobile users more frequently use text messaging for communication than voice calls.
A sender of a new text message enters one or more intended destinations for the message in a user device (e.g., a phone), and also enters the content of the message. The user device of the sender formats the text message into the proper protocol, and sends the text message to a message center in the network over the appropriate signaling channels. One example of a typical message center is an SMS Center (SMSC). The SMSC then attempts to deliver the SMS message to its destination(s).
One particular type of wireless communication network is based on the GSM (Global Systems for Mobile Communications) standard, and is referred to as a GSM network (or GSM/UMTS network). A GSM network typically includes a Base Station Subsystem (which includes the base stations and their controllers) and the core network. The core network includes Mobile Switching Centers (MSC), a Home Location Register (HLR), and one or more message centers, such as an SMSC. The MSC is the primary service delivery node in the GSM network and is responsible for handling voice calls, SMS messages, and other services. The MSC sets up and releases the end-to-end connection, handles mobility and hand-over requirements during the call, etc. The HLR is a central database that stores details of each mobile device that is authorized to use the core network. The HLR stores data for a GSM subscriber, such as GSM services that the subscriber has requested, the present location of subscriber, registration information, etc.
Another type of wireless communication network is based on CDMA2000 standards, and is referred to herein as a CDMA network (or ANSI-41 network). A CDMA network uses CDMA channel access to send voice, data, and signaling between mobile phones and cell sites. The general CDMA2000 standards include CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B. Yet another type of wireless communication network is referred to as an IP Multimedia Subsystem (IMS) network. The IMS is an architectural framework for delivering Internet Protocol (IP) multimedia services. The IMS provides a common core network having a network architecture that allows for various types of access networks. The access network between an IMS device and the IMS network may be a cellular network (e.g., CDMA or GSM), a WLAN (e.g., WiFi or WiMAX), an Ethernet network, or another type of wireless or wireline access network. There may be other types of 3G and 4G communication networks that are used by service providers, such as Long Term Evolution (LTE) networks.
When a mobile device wants access to the GSM network, the mobile device first registers with the network by transmitting a register message to the GSM network. In response to the register message, the GSM network authenticates the mobile device and registers the mobile device for the requested services. The mobile device may then place or receive voice calls, send or receive text messages, etc.
After registration with the GSM network, the mobile device may be turned off, may move out of range of the GSM network, or may otherwise end communication with the GSM network. Even though the mobile device is no longer in communication with the GSM network, the HLR in the GSM network continues to store location mapping data or other data for the mobile device. The stored data indicates that the mobile device is still actively communicating with the GSM network when that is not the case. This may cause problems in the GSM networks or other wireless communication networks for delivering text messages.
For example, assume that a message center in a different network (such as a CDMA network or an IMS network) receives a text message that is addressed to the mobile device. Upon receipt of the text message, the message center (possibly through one or more intermediary devices) queries the HLR in the GSM network for routing information for the text message. Because the HLR stores location mapping data for the mobile device, the HLR responds to the message center with routing information for the text message. This indicates that the mobile device is available to receive the text message over the GSM network when actually the mobile device is not available. In response to the routing information, the message center forwards the text message to the MSC in the GSM network (possibly through one or more intermediary devices). The MSC attempts to deliver the text message to the mobile device, but the delivery attempt will fail because the mobile device is unavailable. The message center then queues the text message for one or more retry attempts. Each retry attempt will also fail because the mobile device is not available over the GSM network even though the HLR indicates that it is available. These failed delivery attempts unfortunately waste network resources.